1. Field of the Invention
The present invention relates to a light-emitting device equipped with a light-emitting element.
2. Description of the Related Art
Small and thin light-emitting elements such as organic electro-luminescence elements are expected to see an expansion of application in fields such as displays and lighting equipments.
Such light-emitting devices equipped with a light-emitting element are often equipped with a reflective film for the purpose of improving light-emission efficiency. For instance, it is described in Japanese Patent Application Laid-open No. 2004-281080 that, in an organic EL element comprising a first electrode, an organic multilayer film and a cathode layered sequentially over a transparent support, the cathode is a mirror-faced reflective film comprising metal.
However, when light is reflected by a reflective film formed from metal, a light illuminating from the back side of the light-emitting device is not transmitted through the reflective film.
Meanwhile, regarding light-emitting devices that are equipped with a light-emitting element, the present inventors have been investigating the application of light-emitting devices to novel uses that utilize the light illuminating from the back side of light-emitting devices. For instance, if a transparent light-emitting device were used as a building material such as of a window glass, the building material would become functional as a lighting device or a display device, while also the external light would be drawn indoors through this building material.
However, in such uses, if a reflective film is used for the purpose of improving the light-emission efficiency, the problem arises, of the light that illuminates from the back side of the light-emitting device being blocked by the reflective film.